The present invention relates generally to a method of yarn piecing in a spinning unit. More specifically, it relates to a method of yarn piecing in a spinning unit having a false-twisting nozzle operating in a pneumatic process for spinning a so-called fasciated yarn, said yarn piecing being accomplished by a so-called splicing method in which a broken yarn end and a mating end of a fiber bundle are pieced up together by interlacing the fibers thereof in the false-twisting zone of the nozzle.
A spun yarn which includes core fibers having substantially no twist and peripheral fibers whose ends bind the core fibers is popularly known as fasciated yarn, and the process for producing such a yarn as the fluid jet process. In this spinning process, fibers of sliver or roving are drafted into a strand or attenuated bundle of fibers by a drafting device comprising plural pairs of drafting rollers. The fibers thus drafted are then transferred into a false-twisting nozzle where they are false-twisted under the influence of rotary streams of fluid such as air as they are advanced continuously through a fiber passage channel formed through said false-twisting nozzle, whereby the bundle of fibers is transformed into a strand of spun yarn which includes, as stated in the above, the core fibers having substantially no twist and the peripheral fibers binding said core fibers.
This spinning process has achieved significant improvements in various respects; in particular, it has shown a remarkable increase in its spinning speed, accounting for much more than 100 m/min. However, this high-speed operation in turn poses a problem or disadvantage in the event of a break in the yarn which must be remedied by a yarn piecing operation. That is, it is extremely difficult, in a fasciated yarn spinning unit operating at a high speed, to allow a broken end of the yarn to overlap with a mating broken end of the fiber bundle in a way suitable for yarn piecing as it is customarily performed on a ring spinning unit for repair of a yarn break. Should piecing of the yarn be accomplished somehow, the resulting yarn may have a loose portion at the joint formed by the yarn piecing due to poor overlapping of the ends, which loose portion makes it difficult to form a yarn package of uniform winding.
Therefore, it has been a general practice in a fasciated yarn spinning unit to employ a knotting method so as to ensure positive yarn piecing, by which a broken yarn end is united by knotting the yarn end with an end of another yarn which is previously provided by twisting a fiber bundle. In this knotting method, however, the knot itself may cause a defect or drawback in the fabrics or knit goods produced in the subsequent weaving or knitting process.
A method which accomplishes yarn piecing by splicing is disclosed in Japanese Unexamined Patent Publication No. 53-35033 (1978), which method comprises the steps of transferring a broken end of the yarn from its package through a false-twisting nozzle in unwinding or reverse direction, holding the yarn end by a front pair of top and bottom drafting rollers, and lapping the yarn end over an end of a fiber bundle. According to this method, it is necessary for the end of the fiber bundle to be positioned correctly at the nip of the front pair of drafting rollers. For example, in the event of entanglement of the fiber bundle around a middle pair of aprons with consequent breaking of the bundle, the fiber bundle is no longer positioned correctly, thus causing failure of the yarn piecing and therefore inviting a decrease in working efficiency.